How important is the industrial revolution for Marx's theory?
Marx's theory was based on his interpretation of the effects of the industrial revolution, so it was essential to it. Marx thought that industrialization had generated two new classes, the bourgeoisie (factory and business owners) and the proletariat (industrial workers). As the effects of industrialization became more entrenched, the working classes got bigger along with the produce of their labor. But because the bourgeoisie was driven solely by the profit motive, working class wages did not increase. Thus they became, to use Marx's word, "alienated" from the value of the things they produced. The more efficient and profitable manufacturing became, the more alienated the proletarians would be. At some point, Marx thought, the situation would become untenable, and the proletarians would rise up as a class and destroy the bourgeoisie, establishing a classless society in its wake. In order for this to happen, the development of industry had to reach a very high state--Marx thought revolution, which was central to his theory, could only occur in an industrialized society. So Marxian theory was essentially a product (albeit an ironic one) of the Industrial Revolution.